[KaeseEs]

Well, no. Currencies as we know them are not only for exchange, but also are supposed to be reasonable stores of value. If a currency loses 85% of its worth in a period of weeks, it has failed at this fundamental task.

Now, for merchants this might not seem to matter, as they might be able to always convert bitcoins to a real currency immediately and never hold them long enough for depreciation to matter, but if the currency is excessively volatile there will never be a buyer at the exchange besides speculators, which prevents the currency from ever being really useful.